On the Electrical main board at home,there is a rotator selector to choose between 3 lines. The guy who installed it said we could switch the line when power goes down on one and said we have ‘3phase’ power.Could someone explain what this arrangement is,I’m confused by what the guy said.

Question

I don’t necessarily understand how it can be termed 3 ph power,because we don’t simply get 3ph to homes as we please,right? Moreover we don’t have any heavy machinery that might even require it. Could someone explain how this arrangement works? Is it just switching between feeders like in a ring fed arrangement of the power system? Or is it actually 3ph power(?)

In: 4

Answer 1

You’re not quite selecting between the three lines.

The electricity that comes from the power plant is three phase (read u/robbak’s explanation how it’s made) and carried by three wires. Each phase is a a pair of those wires. If we call the wires A, B, and C, the three phases are AB, AC, and BC. For most residential power, one of those pairs gets picked and you only have a single phase.

The best way to imagine what’s happening in the switch is that the three phase wires are coming in as the points of a triangle and the switch is choosing which single side of that triangle is supplying your house. You can’t have all three phases feed into a single phase system since that would be a three phase short and blow up the switch (and the closest transformer if you’re unlucky).